A release sheet is utilized as a release sheet used for producing various kinds of synthetic leather product such as synthetic leathers and semi synthetic leathers made of polyurethane resin, and synthetic leathers made of poly-vinyl chloride resin and a decorative laminated plate and the like, wherein the release sheet can be called as a process sheet, and a protect sheet of an adhesive layer of adhesive product.
Conventionally, release sheets prepared by laminating a polyolefin resin such as polypropylene resins and polymethylpenten resins on the surface of a substrate sheet, and forming a release layer, and release sheets prepared by forming a release layer by coating an alkyd resin on the substrate sheet and by providing a emboss processing on the release layer with a emboss roll having a refined uneven on the surface, have been known as the release sheet.
Various kinds of synthetic leather product, decorative laminated plate and the like are produced by extruding a polyurethane resin composition, a poly-vinyl chloride resin composition or the like on the surface of the release layer of these release sheets, transferring an embossing pattern of the surface of the release sheet on the surface of the extruded product, and then peeling off release sheet from the extruded product.
Additionally, as a release sheet used for forming mat style uniformly on the surface of the synthetic leather, a release sheet prepared by forming a release graduated layer on one surface of a substrate paper, by coating an applying liquid of resin composition in which an inorganic and/or organic micro particle are dispersed uniformly in the releasable resin, to form a release layer having refined uneven that an arithmetical mean surface roughness of the surface is 0.5 to 15 μm, has been proposed (Japanese Patent Laid-Open No. 2002-361815).
However, the conventional above-described release sheets are enough to form a mirror style having high gloss on the surface of the formed article obtained by using the release sheet, but are insufficient to form a mat style having low gloss.
When the mat style having low gloss is provided on the surface of the formed article, it is necessary to form a refined and deep uneven uniformly for a large area. But, for making such embossing roll, it was difficult technically.
Additionally, there has been proposed to form a refined uneven of mat style having low gloss on the release layer of the release sheet by coating method instead of the embossing method as described above. However, in this method, it is good to control the gloss, but durability of repeat uses is inferior, uniformity of the film surface is weak, and yield is low, and therefore there is a problem in industrial production. Accordingly, it was not satisfied.